Client not able to pick up

Hi we use patroni 3.1 , pgbouncer, openshift 4.1 , postgres 15.6

Recently we upgraded openshift platform to 4.13 and postgres server is up
and running and now we are witnessing frequent restarts (I can see timeline
added in patronictl history) or whenever failover happened or whenever
system automatically restarted for some reason (etcd logs says "DCS
communication error", postgres log says "received fast shutdown request"
for the same time), those times, fron the client side they are getting
error "cannot execute update in read only transaction" and is stucked in
this msg.

We have a common hostname grocerydb-primary that resolved both master and
standby.

Now, I want to understand two things 1. What could be the reason for
frequent restarts or shutdown and startups 2. Why client is stucked with
the message " cannot execute update in read only transaction" , eventhough
master is up and running.